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Iraqi special forces take part in a drill simulating a hostage rescue operation on Thursday at an Iraqi base in Baghdad. (AFP)

Three car bombs exploded in northern Iraq in Sunday, killing at least four people and injuring 14, according to police officials speaking to AFP.

In Riyadh, a town west of Kirkuk, three policemen were killed and 14 seriously wounded when a suicide bomber detonated a minibus packed with explosives outside Riyadh's police headquarters, according to police Brigadier General Sarhad Qader, who spoke to AFP.

Among the wounded in the 10am blast were nine policemen, including local police chief Major Mundher Ahmed.

Two car bombs targeting Shiite Turkmen territories of the Tuz Khurmatu area killed one more civilian and wounded 27, AFP reported.

Tuz Khurmatu is an ethnically diverse area that stretches from Iraq's eastern border with Iran to it's western front with Syria.

Believed to have triggered Sunday's attacks is the disputes Baghdad and the autonomous Kurdish region have had over land in the north of Iraq, diplomats say.

The explosions occurred in the northern territory where tensions run high over disputed areas of land. According to police sources who spoke to AFP, a dispute over an area of land, which Iraqi Kurdistan wants to incorporate into its territory, caused the attacks. Baghdad has repeatedly blocked the Kurds from accumulating more land, and the tensions in the north are considered to be one of the biggest challenges facing Iraqi domestic security.

In the nearby city of Tuz Khormato, 210 kilometers (130 miles) north of Baghdad, two car bombs exploded early Sunday in a residential area, killing one civilian and wounding 27 others, a police officer told AP.

Sectarian tensions have been on the rise for the last six months and peaked when there were Sunni protests across the country in December. In Iraq, Sunni Arabs are the minority.

Experts on Iraqi domestic politics say there has been a significant lack of effort by the Shiite authorities to address the growing Sunni discontent, which has in turn given more oness on Sunni militant groups to carry out deadly activities.

The outgoing U.N. envoy to Iraq Martin Kobler has warned the violence is "ready to explode", according to AFP.